In general, automatic laboratory equipment for analyzing and/or preparing liquid samples comprises: a computerized central unit that controls various peripherals, such as the feed to a chromatography column, a signal detector at the outlet from the column, and data processing software, for example; and for automating the work of analysis and/or of preparation, a work surface that supports means for supporting the items required for analysis and/or preparation purposes, associated with a sample-taking device capable of transferring liquid from one receptacle to another in a pre-established order under the control of the central unit, the two receptacles being situated on the work surface.
Sample-taking devices are generally constituted by a needle connected to an automatic syringe disposed vertically on a sample-taking arm guided by the central unit in horizontal displacement over the work surface using predefined coordinates, and vertically so as to dip into the liquid to be sampled in the receptacle. Such devices are referred to as XYZ robots, because of their ability to displace the needle in three dimensions.
When the needle is in its low position, the central unit then causes the syringe to suck in or to eject the liquid, depending on whether a sample is to be taken from a receptacle or is to be ejected into another receptacle.
The various receptacles are generally tubes disposed in an array in order to facilitate entering three-dimensional coordinates for each receptacle into the central unit.
Such sampling and analysis systems, and the way in which they operate are described in the literature, and in particular in WO-A-83 04 325.
The automation of analyses has been improved by various systems for organizing the work surface, and in particular systems of carriers for elements for use in filtering and/or purifying samples, in particular the systems described in EP-A-0 180 511 (E. Marteau D'Autry).
The work surface is then fitted with first support means, e.g. supporting preparative cartridges, superposed on second support means, e.g. receiving firstly some test tubes and secondly a waste gutter.
The first support means are movable transversely over the second, and can be displaced linearly under drive from the sampling needle.
It has thus been observed that the needle of an XYZ robot is used not only as means for taking and ejecting liquid samples, but also as a means for imparting linear horizontal displacement to items placed on a carrier.